Liquid crystal display and method of manufacturing the same

ABSTRACT

A liquid crystal display includes a liquid crystal disposed between a first transparent substrate and a second transparent substrate, a first electrode and second electrode which overlie the first transparent substrate and which are used to drive the liquid crystal, one or more layers overlying the first electrode, and one or more layers overlying the second electrode. The correlation between layers disposed between the first electrode and the liquid crystal agrees with the correlation between layers disposed between the second electrode and the liquid crystal.

BACKGROUND

1. Technical Field

The present invention relates to liquid crystal displays and methods ofmanufacturing the liquid crystal displays. The present inventionparticularly relates to a liquid crystal display containing a liquidcrystal controlled by an electric field substantially parallel to atransparent substrate and also relates to a method of manufacturing theliquid crystal display.

2. Related Art

Liquid crystal displays operating in a fringe-field switching (FFS)mode, an in-plane switching (IPS) mode, or another mode are known tohave high contrast and wide viewing angles. The liquid crystal displaysuse electric fields substantially parallel to transparent substrates.

For example, an FFS-mode liquid crystal display includes two transparentsubstrates and a liquid crystal sandwiched therebetween. One of thetransparent substrates has pixel electrodes supplied with displaysignals. A common electrode is disposed above the pixel electrodes withan insulating layer disposed therebetween. The common electrode includesa plurality of linear portions and slit portions alternately arrangedand is applied with a common potential.

FIG. 17 illustrates an example of the arrangement of the pixelelectrodes and the common electrode in cross section. With reference toFIG. 17, a planarization layer 18, which extends over a firsttransparent substrate (not shown) having pixel transistors, underliespixel electrodes 20 made of a transparent conductive material such asindium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrodes20 are covered with an insulating layer 21 made of an inorganic materialsuch as silicon nitride. The insulating layer 21 underlies a commonelectrode which is made of a transparent conductive material such as ITOor IZO, which includes a plurality of linear portions 22E and slitportions 22S alternately arranged, and which is supplied with a commonpotential. The linear portions 22E and the slit portions 22S are coveredwith a first alignment layer 24 made of a polyimide-based resin. Thefirst transparent substrate is attached to a second transparentsubstrate (not shown) having a second alignment layer. A liquid crystalLC is sealed between the first and second transparent substrates. Thefirst transparent substrate and the second transparent substrate have afirst polarizer (not shown) and a second polarizer (not shown),respectively. The transmission axis of the first polarizer isperpendicular to that of the second polarizer. The rubbing direction ofthe first alignment layer 24 and that of a second alignment layer areparallel to the transmission axis of, for example, the first polarizerand are planarly inclined at about five to ten degrees to thelongitudinal direction of the linear portions 22E.

The FFS-mode liquid crystal display is disclosed in JP-A-2002-296611.

The FFS-mode liquid crystal display, which has higher contrast and widerviewing angles as compared to other liquid crystal displays such asTN-mode liquid crystal displays, has a problem in that the center of anoptimum common potential shifts from an initial value during continuousoperation and therefore image sticking is caused. This leads to thedeterioration of the display quality of the FFS-mode liquid crystaldisplay.

The evaluation of the FFS-mode liquid crystal display by experiments hasshown that the shift of the center of the common potential and imagesticking significantly depend on properties of the first alignment layer24.

Suppose attention is focused on members disposed near the firstalignment layer 24 shown in FIG. 17. The following interfaces arepresent on or above the linear portions 22E: the interfaces H betweenthe first alignment layer 24 and the linear portions 22E and theinterface I between the first alignment layer 24 and the liquid crystalLC. On the other hand, the following interfaces are present under theslit portions 22S: the interfaces J between the insulating layer 21 andthe pixel electrodes 20, the interface K between the insulating layer 21and the first alignment layer 24, and the interface L between the firstalignment layer 24 and the liquid crystal LC. That is, the correlationbetween layered members disposed on or above the linear portions 22Edisagrees with the correlation between layered members disposed underthe slit portions 22S.

When electric fields are generated between the pixel electrodes 20 andthe linear portions 22E by the difference between the potential of eachdisplay signal and the common potential, the amount of chargeaccumulated at the interfaces H and I on or above the linear portions22E differs from that at the interfaces J, K, and L under the slitportions 22S. The difference between the charge amounts causesunnecessary direct current components between the pixel electrodes 20and the linear portions 22E. This probably causes the shift of thecenter of the optimum common potential and image sticking.

In order to cope with this problem, another material may be used to formthe first alignment layer 24 or another liquid crystal may be usedinstead of the liquid crystal LC. However, this causes trade-offproblems such as a reduction in orientation force and image sticking dueto excessive charge transfer. Therefore, sufficient improvements havenot been achieved yet.

SUMMARY

An advantage of a first aspect of the invention provides a liquidcrystal display including a liquid crystal disposed between a firsttransparent substrate and a second transparent substrate, a firstelectrode and second electrode which overlie the first transparentsubstrate and which are used to drive the liquid crystal, one or morelayers overlying the first electrode, and one or more layers overlyingthe second electrode. The correlation between layers disposed betweenthe first electrode and the liquid crystal agrees with the correlationbetween layers disposed between the second electrode and the liquidcrystal.

An advantage of a second aspect of the invention provides a liquidcrystal display including a liquid crystal disposed between a firsttransparent substrate and a second transparent substrate, a firstelectrode and second electrode which overlie the first transparentsubstrate and which are used to drive the liquid crystal, one or morelayers overlying the first electrode, and one or more layers overlyingthe second electrode. The amount of charge accumulated at the interfaceor interfaces between layers disposed between the first electrode andthe liquid crystal is substantially equal to the amount of chargeaccumulated at the interface or interfaces between layers disposedbetween the second electrode and the liquid crystal.

The liquid crystal display according to the first or second aspectfurther includes a first inorganic layer extending over the firstelectrode, a second inorganic layer overlying the second electrode, andan alignment layer extending over the second inorganic layer. The secondelectrode includes linear portions and slit portions alternatelyarranged on or above the first inorganic layer.

In the liquid crystal display according to the first or second aspect,portions of the second inorganic layer are disposed only on the linearportions and the alignment layer extends over the first inorganic layer,the second electrode, and the second inorganic layer.

In the liquid crystal display according to the first or second aspect,the second inorganic layer extends over the first inorganic layer, thelinear portions, and the slit portions.

In the liquid crystal display according to the first or second aspect,the first and second inorganic layers are made of the same material.

In the liquid crystal display according to the first or second aspect,the first and second inorganic layers contain a nitrogen compound.

In the liquid crystal display according to the first or second aspect,the first and second inorganic layers contain an oxygen compound.

The liquid crystal display according to the first or second aspectfurther includes an organic layer which is made of an organic materialhaving an imide bond and which extends over the first electrode and alsoincludes an alignment layer made of an organic material having an imidebond. The second electrode includes linear portions and slit portionsalternately arranged on or above the inorganic layer. The alignmentlayer extends over the organic layer, the linear portions, and the slitportions.

The liquid crystal display according to the first or second aspectfurther includes an organic layer which is made of an organic materialsuch as polyamide and which extends over the first electrode and alsoincludes an alignment layer made of an organic material such aspolyamide. The second electrode includes linear portions and slitportions alternately arranged on or above the inorganic layer. Thealignment layer extends over the organic layer, the linear portions, andthe slit portions.

In the liquid crystal display according to the first or second aspect,the organic layer and the alignment layer are made of the same material.

In the liquid crystal display according to the first or second aspect,the first and second electrodes are transparent.

An advantage of a third aspect of the invention provides a method ofmanufacturing the liquid crystal display according to the first orsecond aspect. The method includes forming the first electrode on orabove the first transparent substrate, forming the first inorganic layerover the first electrode, forming a transparent conductive materiallayer over the first inorganic layer, forming the second inorganic layerover the transparent conductive material layer, forming the secondelectrode in such a manner that the transparent conductive materiallayer and the second inorganic layer are patterned together such thatthe linear portions and the slit portions have portions of thetransparent conductive material layer and portions of the secondinorganic layer and are alternately arranged, forming the alignmentlayer over the second electrode, and attaching the second transparentsubstrate to the first transparent substrate to seal the liquid crystalbetween the first transparent substrate and the second transparentsubstrate.

The method according to the third aspect further includes forming aninterconnect layer extending to a region which is disposed on the firsttransparent substrate and which is used to form a terminal section andalso includes forming an electrode over the interconnect layer. Thefirst inorganic layer is formed such that the first electrode is coveredwith the first inorganic layer and the electrode is exposed from thefirst inorganic layer. The transparent conductive material layer isformed so as to cover the first inorganic layer and the exposedelectrode. The transparent conductive material layer and the secondinorganic layer are patterned together such that the second electroderemains and the second inorganic layer is partly removed from theelectrode.

An advantage of a fourth aspect of the invention provides a method ofmanufacturing the liquid crystal display according to the first orsecond aspect. This method includes forming the first electrode on orabove the first transparent substrate; forming the first inorganic layerover the first electrode; forming the second electrode on the firstinorganic layer; forming the second inorganic layer over the firstinorganic layer, the linear portions, and the slit portions; forming thealignment layer over the second inorganic layer; and attaching thesecond transparent substrate to the first transparent substrate to sealthe liquid crystal between the first transparent substrate and thesecond transparent substrate.

In the method according to the third or fourth aspect, the secondinorganic layer is formed by a chemical vapor deposition process.

In the method according to the third or fourth aspect, the secondinorganic layer is formed by a coating process.

In the method according to the third or fourth aspect, the secondinorganic layer is formed by printing an inorganic material.

In the method according to the third or fourth aspect, the first andsecond inorganic layers are made of the same material.

An advantage of a fifth aspect of the invention provides a method ofmanufacturing the liquid crystal display according to the first orsecond aspect. This method includes forming the first electrode on orabove the first transparent substrate; forming the inorganic layer overthe first electrode; forming the second electrode on the first inorganiclayer; forming the alignment layer over the inorganic layer, the linearportions, and the slit portions; rubbing the alignment layer; andattaching the second transparent substrate to the first transparentsubstrate to seal the liquid crystal between the first transparentsubstrate and the second transparent substrate.

An advantage of a sixth aspect of the invention provides a method ofmanufacturing the liquid crystal display according to the first orsecond aspect. This method includes forming the first electrode on orabove the first transparent substrate; forming the inorganic layer overthe first electrode; forming the second electrode on the first inorganiclayer; forming the alignment layer over the inorganic layer, the linearportions, and the slit portions; rubbing the alignment layer; andattaching the second transparent substrate to the first transparentsubstrate to seal the liquid crystal between the first transparentsubstrate and the second transparent substrate.

In the method according to the fifth or sixth aspect, the inorganiclayer and the alignment layer are made of the same material.

In the method according to the fifth or sixth aspect, the alignmentlayer is formed by printing an organic material.

In the method according to the fifth or sixth aspect, the first andsecond electrodes are transparent.

According to the present invention, in an FFS-mode liquid crystaldisplay and a method of manufacturing the display, the shift of thecenter of a common potential and image sticking are prevented, wherebydisplay quality can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a schematic plan view of a liquid crystal display according toa first embodiment of the present invention.

FIG. 2 is an enlarged plan view of pixels arranged in a display sectionincluded in the liquid crystal display shown in FIG. 1.

FIG. 3 is an enlarged plan view of one of terminals arranged in aterminal section included in the liquid crystal display shown in FIG. 1.

FIGS. 4A and 4B are sectional views illustrating a method ofmanufacturing the liquid crystal display according to the firstembodiment.

FIGS. 5A and 5B are sectional views illustrating the method ofmanufacturing the liquid crystal display according to the firstembodiment.

FIGS. 6A and 6B are sectional views illustrating the method ofmanufacturing the liquid crystal display according to the firstembodiment.

FIGS. 7A and 7B are sectional views illustrating the method ofmanufacturing the liquid crystal display according to the firstembodiment.

FIG. 8 is a sectional view of the liquid crystal display according tothe first embodiment.

FIG. 9 is a sectional view illustrating a method of manufacturing aliquid crystal display according to a third embodiment of the presentinvention.

FIG. 10 is a sectional view illustrating the method according to thethird embodiment.

FIG. 11 is a sectional view illustrating the method according to thethird embodiment.

FIG. 12 is a sectional view of the liquid crystal display manufacturedby the method according to the third embodiment.

FIG. 13 is a sectional view illustrating a method of manufacturing aliquid crystal display according to a fourth embodiment of the presentinvention.

FIG. 14 is a sectional view illustrating the method according to thefourth embodiment.

FIG. 15 is a sectional view illustrating the method according to thefourth embodiment.

FIG. 16 is a sectional view of the liquid crystal display manufacturedby the method according to the fourth embodiment.

FIG. 17 is a sectional view of a conventional liquid crystal display.

DESCRIPTION OF EXEMPLARY EMBODIMENTS First Embodiment

A liquid crystal display according to a first embodiment of the presentinvention will now be described with reference to drawings below. FIG. 1is a schematic plan view of the liquid crystal display. FIG. 2 is anenlarged plan view of three of pixels PXL arranged in a display section10A, shown in FIG. 1, operating in an FFS mode. FIG. 3 is an enlargedplan view of one of terminals TL arranged in a terminal section 10Tshown in FIG. 1. FIGS. 1 to 3 show only principal members of the liquidcrystal display for brief description.

In descriptions below, in order to complement the arrangement of firstto fifth contact holes H1 to H5 and openings H6, a gate insulating layer12, an interlayer insulating layer 15, a passivation layer 17, and aplanarization layer 18 are referred to. The correlation between theselayers is shown in the description below of a method of manufacturingthe liquid crystal display.

With reference to FIG. 1, the liquid crystal display includes thedisplay section 10A and the terminal section 10T, the display section10A includes the pixels PXL, and the terminal section 10T includes theterminals TL. With reference to FIG. 2, gate lines 13 supplied with gatesignals, that is, pixel selection signals intersect source lines 16Ssupplied with source signals, that is, display signals and the pixelsPXL are arranged in the display section 10A so as to correspond tointersections of the gate lines 13 and the source lines 16S.

The pixels PXL include pixel transistors TR, such as thin-filmtransistors, arranged on a first transparent substrate 10. The gates ofthe pixel transistors TR are connected to gate electrodes that areportions of the gate lines 13, the sources thereof are connected to thesource lines 16S through the first contact holes H1, and the drainsthereof are connected to drain electrodes 16D through the second contactholes H2. The first and second contact holes H1 and H2 extend throughthe gate insulating layer 12 and the interlayer insulating layer 15. Thedrain electrodes 16D are connected to the pixel electrodes 20 throughthe third and fifth contact holes H3 and H5. The third contact holes H3extend through the passivation layer 17 and the fifth contact holes H5extend through the planarization layer 18.

The pixel electrodes 20 are covered with an insulating layer 21. Theinsulating layer 21 underlies a common electrode 22. The commonelectrode 22 includes a plurality of linear portions 22E and slitportions 22S. The linear portions 22E and slit portions 22S arealternately arranged and extend in parallel to each other. The commonelectrode 22 is connected to a common electrode line (not shown) with acontact hole (not shown). The common electrode line extends near an endportion of the display section 10A and is supplied with a commonpotential.

The pixel electrodes 20, the insulating layer 21, and the linearportions 22E are arranged in that order and form storage capacitorswhich store the source signals for a predetermined time. The drains ofthe pixel transistors TR may be connected to other storage capacitors(not shown) which store the source signals for a predetermined time andwhich supply the source signals to the pixel electrodes 20.

With reference to FIG. 3, an interconnect layer 16T extend above thefirst transparent substrate 10 from the pixels PXL and the like, whichare arranged in the display section 10A, to the terminals TL, which arearranged in the terminal section 10T. The interconnect layer 16T isconnected to, for example, the source lines 16S, which extend in thedisplay section 10A. The interconnect layer 16T is also connected toelectrodes 20T disposed above the interconnect layer 16T through thefourth contact holes H4. The fourth contact holes H4 extend through thepassivation layer 17. The electrodes 20T are covered with the insulatinglayer 21. The insulating layer 21 has the openings H6. The electrodes20T are also connected to external terminals (not shown), such aschips-on-glass (COG) or flexible printed circuits (FPCs), extending fromexternal driving circuits (not shown), through the openings H6.

In the pixels PXL, the pixel transistors TR are turned on in response topixel selection signals supplied from the gate lines 13, whereby displaysignals are supplied to the pixel electrodes 20 through the source lines16S and the pixel transistors TR. This generates electric fieldssubstantially parallel to the first transparent substrate 10 between thepixel electrodes 20 and the linear portions 22E in response to thedisplay signals. The orientation of molecules of a liquid crystal (notshown) is changed depending on the electric fields, whereby opticalcontrol for display is performed. On the other hand, driving signalssuch as pixel selection signals or display signals are supplied to theterminals TL from driving circuits (not shown) through FPCs or the like.

Second Embodiment

A second embodiment of the present invention provides a method ofmanufacturing liquid crystal displays that are the same as the liquidcrystal display according to the first embodiment. The method will nowbe described with reference to drawings below. FIGS. 4A to 7A show oneof pixels PXL arranged in a display section 10A included in each liquidcrystal display in cross section. FIGS. 4B to 7B show one of terminalsTL arranged in a terminal section 10T included in the liquid crystaldisplay in cross section. In FIGS. 4A to 7A and 4B to 7B, the samemembers as those shown in FIGS. 1 to 3 and 17 are denoted by the samereference numerals as those used in FIGS. 1 to 3 and 17.

As shown in FIGS. 4A and 4B, active layers 11 are formed in a region ofthe display section 10A, the region being disposed on a firsttransparent substrate 10 and being used to form the pixels PXL and pixeltransistors TR. A gate insulating layer 12 is formed on the firsttransparent substrate 10 so as to extend over the active layers 11 tothe terminal section 10T. Gate lines 13 are formed on the gateinsulating layer 12 so as to overlap the active layers 11. A commonelectrode line, which is not shown, supplied with a common potential isalso formed on a portion of the gate insulating layer 12 that is locatednear an end portion of the display section 10A.

An interlayer insulating layer 15 is formed on a portion of the gateinsulating layer 12 so as to cover the gate lines 13 and the commonelectrode line, the portion ranging from the display section 10A to theterminal section 10T. Source lines 16S and drain electrodes 16D areformed on a portion of the interlayer insulating layer 15 that isdisposed in the display section 10A, the source lines 16S beingconnected to sources of the active layers 11 through first contact holesH1, the drain electrodes 16D being connected to drains of the activelayers 11 through second contact holes H2.

An interconnect layer 16T is formed in a portion of the terminal section10T that is disposed on the interlayer insulating layer 15. Theinterconnect layer 16T extends from the display section 10A. The sourcelines 16S, the drain electrodes 16D, and the interconnect layer 16T arelaminates formed together from a single layer including, for example, atitanium sub-layer, aluminum sub-layer, and titanium sub-layer arrangedin that order. A passivation layer 17 is formed on the interlayerinsulating layer 15 so as to cover the source lines 16S, the drainelectrodes 16D, and the interconnect layer 16T. The passivation layer 17is a silicon nitride film formed at, for example, 300° C. to 400° C.

The passivation layer 17 is masked with a resist layer (not shown) andis then dry-etched, whereby third contact holes H3 and fifth contactholes H5 are formed in the passivation layer 17. The drain electrodes16D are exposed through the third contact holes H3. The interconnectlayer 16T is exposed through the fifth contact holes H5.

After the resist layer is removed, a planarization layer 18 such as anorganic layer is formed over the walls of the third and fifth contactholes H3 and H5 and the passivation layer 17. The planarization layer 18is masked with another resist layer (not shown) and is then dry-etched,whereby fourth contact holes H4 are formed in the planarization layer18. The fourth contact holes H4 are connected to the third contact holesH3 and therefore the drain electrodes 16D are exposed through the thirdand fourth contact holes H3 and H4. The planarization layer 18 is partlyremoved from the terminal section 10T, so that interconnect layer 16T isexposed through the fifth contact holes H5 again.

Pixel electrodes 20 are formed on the planarization layer 18 so as toextend through the fourth contact holes H4 to the drain electrodes 16D.The pixel electrodes 20 are an example of first electrodes specified inthe claims. Electrodes 20T are formed in the terminal section 10T so asto be connected to the interconnect layer 16T through the fifth contactholes H5. The electrodes 20T are an example of electrodes specified inthe claims. The pixel electrodes 20 and the electrodes 20T are formedfrom a transparent conductive material such as ITO or IZO by patterning.The pixel electrodes 20 and the electrodes 20T preferably have athickness of about 100 nm.

An insulating layer 21 is formed over a portion of the planarizationlayer 18 that is disposed in the display section 10A and a portion ofthe passivation layer 17 that is disposed in the terminal section 10T,whereby the pixel electrodes 20 and the electrodes 20T are covered withthe insulating layer 21. The insulating layer 21 is an inorganic filmsuch as a silicon nitride film formed at a low temperature of about 200°C. The insulating layer 21 has portions which are disposed betweenlinear portions 22E disposed in a common electrode 22 and which have athickness of about 2 to 4 μm so as to form optimum capacitors. Theinsulating layer 21 is an example of a first inorganic layer specifiedin the claims.

A resist layer (not shown) having open portions corresponding to theelectrodes 20T are formed on the insulating layer 21. The insulatinglayer 21 is dry-etched using this resist layer as a mask, wherebyopenings H6 are formed in the insulating layer 21. The openings H6 areconnected to the fifth contact holes H5, which are disposed in theterminal section 10T, and therefore the electrodes 20T are exposedthrough the openings H6.

After this resist layer is removed, a transparent conductive materiallayer 22A made of ITO or IZO is formed over the insulating layer 21,which extends from the display section 10A to the terminal section 10T,as shown in FIGS. 5A and 5B.

An inorganic layer 23A made of silicon nitride or the like is formedover the transparent conductive material layer 22A, which extends fromthe display section 10A to the terminal section 10T, by a chemical vapordeposition (CVD) process or a coating process such as a spin coatingprocess or a printing process. The thickness of the inorganic layer 23Ais not particularly limited and is preferably small in consideration ofthat bumps cause difficulties in rubbing a first alignment layer 24. Theinorganic layer 23A preferably has a thickness of, for example, 50 nm orless. The inorganic layer 23A and the insulating layer 21 may be made ofan inorganic material other than silicon nitride and are preferably madeof the same material.

As shown in FIGS. 6A and 6B, the inorganic layer 23A and the insulatinglayer 21 are patterned by dry etching using resist layers (not shown) asmasks. These resist layers cover only regions used to form the linearportions 22E.

This allows the common electrode 22 to be formed on the insulating layer21 such that the linear portions 22E and slit portions 22S arealternately arranged and extend in parallel to each other and alsoallows inorganic layer portions 23 to be formed only on the linearportions 22E. None of the inorganic layer portions 23 is present in theterminal section 10T. As described above, the common electrode 22 andthe inorganic layer portions 23 arranged thereon can be achieved bypatterning in a single dry etching step. The inorganic layer 23A is anexample of a second inorganic layer specified in the claims. The commonelectrode 22 is an example of a second electrode specified in theclaims.

In this embodiment, the common electrode 22 and the inorganic layerportions 23 arranged thereon can be achieved by patterning in a singledry etching step as described above. Therefore, the method is simplerand less in manufacturing cost as compared to the case where thetransparent conductive material layer 22A is formed, the commonelectrode 22 is formed by patterning the transparent conductive materiallayer 22A, the inorganic layer 23A is formed over the common electrode22, and the inorganic layer portions 23 are then formed only on thelinear portions 22E by patterning the inorganic layer 23A.

As shown in FIGS. 7A and 7B, the first alignment layer 24 is formed overthe common electrode 22 and the inorganic layer portions 23. The firstalignment layer 24 is made of a polyimide-based resin. The rubbingdirection of the first alignment layer 24 is planarly inclined at aboutfive to ten degrees to the longitudinal direction of the linear portions22E. The first alignment layer 24 is an example of an alignment layerspecified in the claims.

A second transparent substrate 30 is attached to the first transparentsubstrate 10. A liquid crystal LC, such as a nematic liquid crystal,having positive dielectric anisotropy is sealed between the first andsecond transparent substrates 10 and 30. The second transparentsubstrate 30 has a surface facing the first transparent substrate 10 andthis surface carries a black matrix (not shown), a color filter 31, anda second alignment layer 32 extending thereover. The second alignmentlayer 32 is made of a polyimide-based resin. The rubbing direction ofthe second alignment layer 32 is parallel to that of the first alignmentlayer 24.

In a portion of the above procedure, a first polarizer PL1 is providedon a surface of the first transparent substrate 10 that faces a lightsource BL. The transmission axis of the first polarizer PL1 is parallelto the rubbing direction of the first alignment layer 24. In a portionof the procedure, a second polarizer PL2 is provided on a surface of thesecond transparent substrate 30 that oppositely faces the firsttransparent substrate 10. The transmission axis of the second polarizerPL2 is perpendicular to the rubbing direction of the first polarizerPL1.

A laminate including the first and second transparent substrates 10 and30 and the above members is divided into the liquid crystal displays byscribing or breaking.

Suppose attention is focused on the correlation between layered membersdisposed between the liquid crystal LC and pixel electrodes 20 of thedisplay section 10A of each liquid crystal display completed asdescribed above. The correlation between layered members disposed on orabove the linear portions 22E agrees with the correlation betweenlayered members disposed under the slit portions 22S. This is the resultachieved by the deposition of the inorganic layer portions 23 on thelinear portions 22E.

The agreement of these correlations will now be described with referenceto a drawing below. FIG. 8 is a partly enlarged view showing membersarranged near the first alignment layer 24 shown in FIG. 7. In eachregion containing a corresponding one of the linear portions 22E, thefollowing interfaces are arranged on the linear portion 22E in thisorder as shown in FIG. 8: the interface A between the linear portion22E, which is made of a transparent conductive material such as ITO, anda corresponding one of the inorganic layer portions 23, which are madeof silicon nitride or the like; the interface B between the inorganiclayer portion 23 and the first alignment layer 24, which is made of apolyimide-based resin; and the interface C between the first alignmentlayer 24 and the liquid crystal LC.

On the other hand, in each region containing a corresponding one of theslit portions 22S, the following interfaces are arranged in this order:the interface D between a corresponding one of the pixel electrodes 20,which are made of a transparent conductive material such as ITO, and theinsulating layer 21, which is made of an inorganic material such assilicon nitride; the interface E between the insulating layer 21 and thefirst alignment layer 24, which is made of a polyimide-based resin; andthe interface F between the insulating layer 21 and the liquid crystalLC. That is, the correlation between layered members disposed on orabove the linear portion 22E agrees with the correlation between layeredmembers disposed under the slit portion 22S.

This configuration allows the amount of charge accumulated at theinterfaces A, B, and C present in the linear portion 22E-containingregion to be substantially equal to the amount of charge accumulated atthe interfaces D, E, and F present in the slit portion 22S-containingregion when an electric field is generated between the pixel electrode20 and the linear portion 22E by the difference between the potential ofa display signal and the common potential. That is, this configurationcreates a symmetry in charge amount between these regions. Experimentsperformed by the inventors have shown that the symmetry is achievedindependently of the thickness of the insulating layer 21, the inorganiclayer portions 23, or the first alignment layer 24.

If the correlation between the layered members disposed on or above thelinear portion 22E disagrees with the correlation between the layeredmembers disposed under the slit portion 22S, a difference in chargeamount is created between these regions with time after an electricfield is generated between the pixel electrode 20 and the linear portion22E by the difference between the potential of a display signal and thecommon potential. Therefore, the symmetry in charge amount between theseregions is broken. This causes a direct current component between thepixel electrode 20 and the linear portion 22E to shift the center of anoptimum common potential. The center of an optimum common potential thatminimizes flickers is shifted by 150 mV during electric conduction for,for example, ten hours. Therefore, the fact that the center of such anoptimum common potential that minimizes flickers is not shifted duringelectrical conduction suggests that the symmetry in charge amountbetween these regions is substantially maintained.

The symmetry prevents an unnecessary direct current component from beinggenerated between the pixel electrode 20 and the linear portion 22E;hence, an electric field corresponding only to a display signal isgenerated. Therefore, the shift of the center of an optimum commonpotential and image sticking, which occur in conventional FFS-modeliquid crystal displays, are prevented. This allows the liquid crystaldisplay to have display quality higher than that of conventional ones.

The liquid crystal display, which has the above configuration, can bemanufactured through simple steps at low cost. This is because thecommon electrode 22 and the inorganic layer portions 23 are formedtogether by patterning in a single dry etching step.

The material used to form the first alignment layer 24 or the liquidcrystal LC need not be changed to achieve the above advantages. Thiseliminates trade-off problems such as a reduction in orientation forceand image sticking due to excessive charge transfer.

In this embodiment, the slit portions 22S and the linear portions 22Eare not limited to those shown in FIG. 2. The longitudinal direction ofthe slit portions 22S and that of the linear portions 22E may beparallel to the source lines 16S or may diagonally intersect the gatelines 13. The slit portions 22S and the linear portions 22E may have alength sufficient to extend over some of the pixels PXL. The slitportions 22S and the linear portions 22E need not be linear and may havea curved shape, a wavy shape, or a zigzag shape. Alternatively, the slitportions 22S and the linear portions 22E may have a comb shape. Thepresent invention is not limited to the second embodiment and may beapplied to a liquid crystal display including a first electrodefunctioning as a common electrode and second electrodes functioning aspixel electrodes. That is, the following members may be formed in thisorder: a common electrode is formed on a planarization layer 18, aninsulating layer 21 is formed on this planarization layer 18, and pixelelectrodes each including a plurality of linear portions and slitportions substantially identical to those of that common electrode 22are formed on this insulating layer 21. In this case, inorganic layerportions 23 are each formed on a corresponding one of these linearportions. This configuration is also effective in achieving the aboveadvantages.

Third Embodiment

A third embodiment of the present invention provides a method ofmanufacturing liquid crystal displays. The method will now be describedwith reference to drawings below. FIGS. 4A, and 9 to 11 show one ofpixels PXL arranged in a display section 10A included in each liquidcrystal display. In FIGS. 9 to 11, the same members as those shown inFIGS. 1 to 8 and 17 are denoted by the same reference numerals as thoseused in FIGS. 1 to 8 and 17.

As shown in FIG. 4A, active layers 11 are formed in a region of thedisplay section 10A, the region being disposed on a first transparentsubstrate 10 and being used to form the pixels PXL and pixel transistorsTR. A gate insulating layer 12 is formed on the first transparentsubstrate 10 so as to cover the active layers 11. Gate lines 13 areformed on the gate insulating layer 12 so as to overlap the activelayers 11. A common electrode line, which is not shown, supplied with acommon potential is also formed on a portion of the gate insulatinglayer 12 that is located near an end portion of the display section 10A.

An interlayer insulating layer 15 is formed on a portion of the gateinsulating layer 12 so as to cover the gate lines 13 and the commonelectrode line, the portion being disposed in the display section 10A.Source lines 16S and drain electrodes 16D are formed on the interlayerinsulating layer 15, the source lines 16S being connected to sources ofthe active layers 11 through first contact holes H1, the drainelectrodes 16D being connected to drains of the active layers 11 throughsecond contact holes H2.

The source lines 16S and the drain electrodes 16D are laminates formedtogether from a single layer including, for example, a titaniumsub-layer, aluminum sub-layer, and titanium sub-layer arranged in thatorder. A passivation layer 17 is formed on the interlayer insulatinglayer 15 so as to cover the source lines 16S and the drain electrodes16D. The passivation layer 17 is a silicon nitride film formed at, forexample, 300° C. to 400° C.

The passivation layer 17 is masked with a resist layer (not shown) andis then dry-etched, whereby third contact holes H3 are formed in thepassivation layer 17. The drain electrodes 16D are exposed through thethird contact holes H3.

After the resist layer is removed, a planarization layer 18 such as anorganic layer is formed over the walls of the third contact holes H3 andthe passivation layer 17. The planarization layer 18 is masked withanother resist layer (not shown) and is then dry-etched, whereby fourthcontact holes H4 are formed in the planarization layer 18. The fourthcontact holes H4 are connected to the third contact holes H3 andtherefore the drain electrodes 16D are exposed through the third andfourth contact holes H3 and H4.

Pixel electrodes 20 are formed on the planarization layer 18 so as toextend through the fourth contact holes H4 to the drain electrodes 16D.The pixel electrodes 20 are an example of first electrodes specified inthe claims. The pixel electrodes 20 are formed from a transparentconductive material such as ITO or IZO by patterning. The pixelelectrodes 20 preferably have a thickness of about 100 nm.

An insulating layer 21 is formed on the planarization layer 18 so as tocover the pixel electrodes 20. The insulating layer 21 is a nitrogencompound-containing inorganic film such as a silicon nitride film formedat a low temperature of about 200° C. The insulating layer 21 is anexample of a first inorganic layer specified in the claims.

As shown in FIG. 9, a common electrode 22 is formed on the insulatinglayer 21. The common electrode 22 includes linear portions 22E and slitportions 22S which are alternately arranged and which extend in parallelto each other and also allows inorganic layer portions 23. The commonelectrode 22 is formed from a transparent conductive material such asITO or IZO by patterning.

As shown in FIG. 10, an inorganic layer 23 is formed over the insulatinglayer 21, the linear portions 22E, and the slit portions 22S. Theinorganic layer 23 contains a nitrogen compound such as silicon nitrideand is formed by a CVD process or another deposition process. Thethickness of the inorganic layer 23 is not particularly limited and is,for example, about 50 nm or less. The inorganic layer 23 is an exampleof a second inorganic layer specified in the claims.

The inorganic layer 23 and the insulating layer 21 may be inorganicfilms other than silicon nitride films and are preferably formed fromthe same material.

Alternatively, the inorganic layer 23 and the insulating layer 21 maycontain an oxygen compound such as silicon dioxide or a compound, suchas silicon oxynitride, containing oxygen and nitrogen.

An example of a process, other than the CVD process, for forming theinorganic layer 23 is as follows: paste containing silicon and anorganic material is formed into a layer by a coating process such as aspin coating process or a printing process and is then baked, whereby asilicon dioxide layer, that is, the inorganic layer 23 is obtained.

The inorganic layer 23 is preferably formed by the printing process,which is an example of the coating process, or in such a manner that aninorganic material is printed (for example, screen-printed orrelief-printed) to form a predetermined pattern. This is because the useof the printing process eliminates a patterning step that is necessaryfor the CVD process or another coating process to form openings in aportion of the inorganic layer 23 that extends over the terminals TL,which are arranged in the terminal section 10T shown in FIG. 1; hence,the method can be simplified.

As shown in FIG. 11, a first alignment layer 24 is formed over theinorganic layer portions 23. The first alignment layer 24 is made of apolyimide-based resin. The rubbing direction of the first alignmentlayer 24 is planarly inclined at about five to ten degrees to thelongitudinal direction of the linear portions 22E. The first alignmentlayer 24 is an example of an alignment layer specified in the claims.

A second transparent substrate 30 is attached to the first transparentsubstrate 10. A liquid crystal LC, such as a nematic liquid crystal,having positive dielectric anisotropy is sealed between the first andsecond transparent substrates 10 and 30. The second transparentsubstrate 30 has a surface facing the first transparent substrate 10 andthis surface carries a black matrix (not shown), a color filter 31, anda second alignment layer 32 extending thereover. The second alignmentlayer 32 is made of a polyimide-based resin. The rubbing direction ofthe second alignment layer 32 is parallel to that of the first alignmentlayer 24.

In a portion of the above procedure, a first polarizer PL1 is providedon a surface of the first transparent substrate 10 that faces a lightsource BL. The transmission axis of the first polarizer PL1 is parallelto the rubbing direction of the first alignment layer 24. In a portionof the procedure, a second polarizer PL2 is provided on a surface of thesecond transparent substrate 30 that oppositely faces the firsttransparent substrate 10. The transmission axis of the second polarizerPL2 is perpendicular to the rubbing direction of the first polarizerPL1.

A laminate including the first and second transparent substrates 10 and30 and the above members is divided into the liquid crystal displays byscribing or breaking.

Suppose attention is focused on the correlation between layered membersdisposed between the liquid crystal LC and pixel electrodes 20 of thedisplay section 10A of each liquid crystal display completed asdescribed above. The correlation between layered members disposed on orabove the linear portions 22E agrees with the correlation betweenlayered members disposed under the slit portions 22S. This is the resultachieved by the deposition of the inorganic layer portions 23 over thelinear portions 22E and the slit portions 22S.

The agreement of these correlations will now be described with referenceto a drawing below. FIG. 12 is a partly enlarged view showing membersarranged near the first alignment layer 24 shown in FIG. 11. In eachregion containing a corresponding one of the linear portions 22E, thefollowing interfaces are arranged on the linear portion 22E in thisorder as shown in FIG. 12: the interface A′ between the linear portion22E, which is made of a transparent conductive material such as ITO, andthe inorganic layer 23, which is made of silicon nitride or the like;the interface B′ between the inorganic layer 23 and the first alignmentlayer 24, which is made of a polyimide-based resin; and the interface C′between the first alignment layer 24 and the liquid crystal LC.

On the other hand, in each region containing a corresponding one of theslit portions 22S, the following interfaces are arranged in this order:the interface D′ between a corresponding one of the pixel electrodes 20,which are made of a transparent conductive material such as ITO, and theinsulating layer 21, which is made of an inorganic material such assilicon nitride; the interface E′ between the inorganic layer 23, whichis made of silicon nitride or the like, and the first alignment layer24, which is made of a polyimide-based resin; and the interface F′between the first alignment layer 24 and the liquid crystal LC. That is,the correlation between layered members disposed on or above the linearportion 22E agrees with the correlation between layered members disposedunder the slit portion 22S.

Since the insulating layer 21 and the inorganic layer 23 are made of thesame inorganic material and a difference therebetween due to a formingprocess is negligible, the following interface is left out ofconsideration: the interface between a portion of the insulating layer21 that is disposed under the slit portion 22S and a portion of theinorganic layer 23 that is disposed in the slit portion 22S.

This configuration allows the amount of charge accumulated at theinterfaces A′, B′, and C′ present in the linear portion 22E-containingregion to be substantially equal to the amount of charge accumulated atthe interfaces D′, E′, and F′ present in the slit portion 22S-containingregion when an electric field is generated between the pixel electrode20 and the linear portion 22E by the difference between the potential ofa display signal and a common potential. That is, this configurationcreates a symmetry in charge amount between these regions. Experimentsperformed by the inventors have shown that the symmetry is achievedindependently of the thickness of the insulating layer 21, the inorganiclayer 23, or the first alignment layer 24.

The symmetry prevents an unnecessary direct current component from beinggenerated between the pixel electrode 20 and the linear portion 22E;hence, an electric field corresponding only to a display signal isgenerated. Therefore, the shift of the center of an optimum commonpotential and image sticking, which occur in conventional FFS-modeliquid crystal displays, are prevented. This allows the liquid crystaldisplay to have display quality higher than that of conventional ones.

The material used to form the first alignment layer 24 or the liquidcrystal LC need not be changed to achieve the above advantages. Thiseliminates trade-off problems such as a reduction in orientation forceand image sticking due to excessive charge transfer.

In this embodiment, the inorganic layer 23 and the insulating layer 21are made of the same material. The present invention is not limited tothis configuration. The inorganic layer 23 and the insulating layer 21may be made of different materials that prevent unnecessary charge frombeing accumulated at the interface between these layers, although theabove advantages are reduced. When the insulating layer 21 is made ofsilicon nitride, the inorganic layer 23 may be made of, for example,silicon dioxide.

The slit portions 22S and the linear portions 22E are not limited tothose shown in FIG. 2. The longitudinal direction of the slit portions22S and that of the linear portions 22E may be parallel to the sourcelines 16S or may diagonally intersect the gate lines 13. The slitportions 22S and the linear portions 22E may have a length sufficient toextend over some of the pixels PXL. The slit portions 22S and the linearportions 22E need not be linear and may have a curved shape, a wavyshape, or a zigzag shape. Alternatively, the slit portions 22S and thelinear portions 22E may have a comb shape.

The present invention is not limited to this embodiment and may beapplied to a liquid crystal display including a common electrodecorresponding to a first electrode and pixel electrodes corresponding tosecond electrodes. That is, the following members may be formed in thisorder: this common electrode is formed on a planarization layer 18, aninsulating layer 21 is formed on this common electrode, and these pixelelectrodes each including a plurality of linear portions and slitportions substantially identical to those of that common electrode 22are formed on this insulating layer 21. In this case, an inorganic layer23 is formed over this insulating layer 21 and the linear portions andslit portions of these pixel electrodes. This configuration is alsoeffective in achieving the above advantages.

Fourth Embodiment

A fourth embodiment of the present invention provides a method ofmanufacturing liquid crystal displays. The method will now be describedwith reference to drawings below. FIGS. 4A, and 13 to 15 show one ofpixels PXL arranged in a display section 10A included in each liquidcrystal display. In FIGS. 13 to 15, the same members as those shown inFIGS. 1 to 12 and 17 are denoted by the same reference numerals as thoseused in FIGS. 1 to 12 and 17.

As shown in FIG. 4A, active layers 11 are formed in a region of thedisplay section 10A, the region being disposed on a first transparentsubstrate 10 and being used to form the pixels PXL and pixel transistorsTR. A gate insulating layer 12 is formed on the first transparentsubstrate 10 so as to cover the active layers 11. Gate lines 13 areformed on the gate insulating layer 12 so as to overlap the activelayers 11. A common electrode line, which is not shown, supplied with acommon potential is also formed on a portion of the gate insulatinglayer 12 that is located near an end portion of the display section 10A.

An interlayer insulating layer 15 is formed on a portion of the gateinsulating layer 12 so as to cover the gate lines 13 and the commonelectrode line, the portion being disposed in the display section 10A.Source lines 16S and drain electrodes 16D are formed on the interlayerinsulating layer 15, the source lines 16S being connected to sources ofthe active layers 11 through first contact holes H1, the drainelectrodes 16D being connected to drains of the active layers 11 throughsecond contact holes H2.

The source lines 16S and the drain electrodes 16D are laminates formedtogether from a single layer including, for example, a titaniumsub-layer, aluminum sub-layer, and titanium sub-layer arranged in thatorder. A passivation layer 17 is formed on the interlayer insulatinglayer 15 so as to cover the source lines 16S and the drain electrodes16D. The passivation layer 17 is a silicon nitride film formed at, forexample, 300° C. to 400° C.

The passivation layer 17 is masked with a resist layer (not shown) andis then dry-etched, whereby third contact holes H3 are formed in thepassivation layer 17. The drain electrodes 16D are exposed through thethird contact holes H3.

After the resist layer is removed, a planarization layer 18 such as anorganic layer is formed over the walls of the third contact holes H3 andthe passivation layer 17. The planarization layer 18 is masked withanother resist layer (not shown) and is then dry-etched, whereby fourthcontact holes H4 are formed in the planarization layer 18. The fourthcontact holes H4 are connected to the third contact holes H3 andtherefore the drain electrodes 16D are exposed through the third andfourth contact holes H3 and H4.

Pixel electrodes 20 are formed on the planarization layer 18 so as toextend through the fourth contact holes H4 to the drain electrodes 16D.The pixel electrodes 20 are an example of first electrodes specified inthe claims. The pixel electrodes 20 are formed from a transparentconductive material such as ITO or IZO by patterning. The pixelelectrodes 20 preferably have a thickness of about 100 nm.

An organic insulating layer 21 is formed on the planarization layer 18so as to cover the pixel electrodes 20. The organic insulating layer 21is made of an organic material, such as a polyimide-based resin, havingan imide bond. The thickness of the organic insulating layer 21 is notparticularly limited and is, for example, about 150 nm. The organicinsulating layer 21 is an example of a first inorganic layer specifiedin the claims.

As shown in FIG. 13, a common electrode 22 is formed on the organicinsulating layer 21. The common electrode 22 includes linear portions22E and slit portions 22S which are alternately arranged and whichextend in parallel to each other and also allows inorganic layerportions 23. The common electrode 22 is formed from a transparentconductive material such as ITO or IZO by patterning.

As shown in FIG. 14, an organic layer 23A is formed over the organicinsulating layer 21, the linear portions 22E, and the slit portions 22S.The organic layer 23A is made of an organic material having an imidebond or a polyimide-based resin. The thickness of the organic layer 23Ais not particularly limited and is, for example, about 70 nm. Theorganic layer 23A is an example of a second inorganic layer specified inthe claims.

The organic layer 23A is formed by a coating process such as a spincoating process using an organic material or a printing process forprinting an organic material. The organic layer 23A is preferably formedby the printing process, which is an example of the coating process, orin such a manner that an inorganic material is printed to form apredetermined pattern. Examples of the printing process include a screenprinting process and an ink jet printing process. The use of theprinting process eliminates a patterning step that is necessary forother coating processes to remove the organic layer 23A from theterminal section 10T shown in FIG. 1; hence, the method can besimplified.

The organic layer 23A is rubbed in a predetermined alignment direction,whereby the organic layer 23A is converted into a first alignment layer23. The rubbing direction of the first alignment layer 23 is planarlyinclined at about five to ten degrees to the longitudinal direction ofthe linear portions 22E. The first alignment layer 23 is an example ofan alignment layer specified in the claims.

The organic insulating layer 21 and the first alignment layer 23, whichis derived from the organic layer 23A, may be made of an organicmaterial, other than a polyimide-based resin, having an imide bond andare preferably made of the same material. Alternatively, the organicinsulating layer 21 and the first alignment layer 23 may be made of apolyamide-based resin such as a polyamic acid resin.

As shown in FIG. 15, a second transparent substrate 30 is attached tothe first transparent substrate 10. A liquid crystal LC, such as anematic liquid crystal, having positive dielectric anisotropy is sealedbetween the first and second transparent substrates 10 and 30. Thesecond transparent substrate 30 has a surface facing the firsttransparent substrate 10 and this surface carries a black matrix (notshown), a color filter 31, and a second alignment layer 32 extendingthereover. The second alignment layer 32 is made of a polyimide-basedresin. The rubbing direction of the second alignment layer 32 isparallel to that of the first alignment layer 23.

In a portion of the above procedure, a first polarizer PL1 is providedon a surface of the first transparent substrate 10 that faces a lightsource BL. The transmission axis of the first polarizer PL1 is parallelto the rubbing direction of the first alignment layer 23. In a portionof the procedure, a second polarizer PL2 is provided on a surface of thesecond transparent substrate 30 that oppositely faces the firsttransparent substrate 10. The transmission axis of the second polarizerPL2 is perpendicular to the rubbing direction of the first polarizerPL1.

A laminate including the first and second transparent substrates 10 and30 and the above members is divided into the liquid crystal displays byscribing or breaking.

Suppose attention is focused on the correlation between layered membersdisposed between the liquid crystal LC and pixel electrodes 20 of thedisplay section 10A of each liquid crystal display completed asdescribed above. The correlation between layered members disposed on orabove the linear portions 22E agrees with the correlation betweenlayered members disposed under the slit portions 22S. This is the resultachieved by the presence of the organic insulating layer 21 between thecommon electrode 22 and the pixel electrodes 20 and the presence of thefirst alignment layer 23, which is derived from the organic layer 23A,over the linear portions 22E and the slit portions 22S.

The agreement of these correlations will now be described with referenceto a drawing below. FIG. 16 is a partly enlarged view showing membersarranged near the first alignment layer 23 shown in FIG. 15. In eachregion containing a corresponding one of the linear portions 22E, thefollowing interfaces are arranged on the linear portion 22E in thisorder as shown in FIG. 16: the interface A″ between the linear portion22E, which is made of a transparent conductive material such as ITO, andthe first alignment layer 23, which is made of an organic material suchas a polyimide-based resin, and the interface B″ between the firstalignment layer 23 and the liquid crystal LC.

On the other hand, in each region containing a corresponding one of theslit portions 22S, the following interfaces are arranged in this order:the interface D″ between a corresponding one of the pixel electrodes 20,which are made of a transparent conductive material such as ITO, and theorganic insulating layer 21, which is made of an organic material suchas a polyimide-based resin, and the interface E″ between the firstalignment layer 23, which is made of an organic material such as apolyimide-based resin, and the liquid crystal LC. That is, thecorrelation between layered members disposed on or above the linearportion 22E agrees with the correlation between layered members disposedunder the slit portion 22S.

Since the organic insulating layer 21 and the first alignment layer 23are made of the same inorganic material and a difference therebetweendue to a forming process is negligible, the following interface is leftout of consideration: the interface between a portion of the organicinsulating layer 21 that is disposed under the slit portion 22S and aportion of the first alignment layer 23 that is disposed in the slitportion 22S.

This configuration allows the amount of charge accumulated at theinterfaces A″ and B″ present in the linear portion 22E-containing regionto be substantially equal to the amount of charge accumulated at theinterfaces D″ and E″ present in the slit portion 22S-containing regionwhen an electric field is generated between the pixel electrode 20 andthe linear portion 22E by the difference between the potential of adisplay signal and a common potential. That is, this configurationcreates a symmetry in charge amount between these regions. Experimentsperformed by the inventors have shown that the symmetry is achievedindependently of the thickness of the organic insulating layer 21 or thefirst alignment layer 23.

The symmetry prevents an unnecessary direct current component from beinggenerated between the pixel electrode 20 and the linear portion 22E;hence, an electric field corresponding only to a display signal isgenerated.

Therefore, the shift of the center of an optimum common potential andimage sticking, which occur in conventional FFS-mode liquid crystaldisplays, are prevented. This allows the liquid crystal display to havedisplay quality higher than that of conventional ones.

The material used to form the first alignment layer 23 or the liquidcrystal LC need not be changed to achieve the above advantages. Thiseliminates trade-off problems such as a reduction in orientation forceand image sticking due to excessive charge transfer.

In this embodiment, the organic insulating layer 21 and the firstalignment layer 23, which is derived from the organic layer 23A, aremade of the same material. The present invention is not limited to thisconfiguration. The organic insulating layer 21 and the first alignmentlayer 23 may be made of different organic materials that preventunnecessary charge from being accumulated at the interface between theselayers, although the above advantages are reduced. When the firstalignment layer 23, which is derived from the organic layer 23A, is madeof an organic material such as a polyimide-based resin, the organicinsulating layer 21 may be a polyamide-based resin such as a polyamicacid resin.

The slit portions 22S and the linear portions 22E are not limited tothose shown in FIG. 2. The longitudinal direction of the slit portions22S and that of the linear portions 22E may be parallel to the sourcelines 16S or may diagonally intersect the gate lines 13. The slitportions 22S and the linear portions 22E may have a length sufficient toextend over some of the pixels PXL. The slit portions 22S and the linearportions 22E need not be linear and may have a curved shape, a wavyshape, or a zigzag shape. Alternatively, the slit portions 22S and thelinear portions 22E may have a comb shape.

The present invention is not limited to this embodiment and may beapplied to a liquid crystal display including a common electrodecorresponding to a first electrode and pixel electrodes corresponding tosecond electrodes. That is, the following members may be formed in thisorder: this common electrode is formed on a planarization layer 18, anorganic insulating layer 21 is formed on this common electrode, andthese pixel electrodes each including a plurality of linear portions andslit portions substantially identical to those of that common electrode22 are formed on this organic insulating layer 21. In this case, a firstalignment layer 23 is formed over this organic insulating layer 21 andthe linear portions and slit portions of these pixel electrodes. Thisconfiguration is also effective in achieving the above advantages.

In this liquid crystal display, which includes this common electrodecorresponding to a first electrode and these pixel electrodescorresponding to second electrodes, contact holes need to be formed inthis organic insulating layer 21 such that these pixel electrodes areeach connected to a pixel transistor TR included in a corresponding oneof pixels PXL.

If an organic insulating layer 121, shown in FIG. 17, made of an organicmaterial such as silicon nitride is used instead of this organicinsulating layer 21, an etching step is necessary to pattern the organicinsulating layer 121. This causes an increase in manufacturing cost.

According to this embodiment, this organic insulating layer 21 is madeof a photosensitive organic material and the contact holes can be formedin such a manner that this insulating layer 21 is patterned by a simplephotolithographic process; hence, the etching step is not necessary.

The entire disclosure of Japanese Patent Application No. 2008-063711,filed Mar. 13, 2008, 2008-063710, filed Mar. 13, 2008 and 2008-070792,filed Mar. 19, 2008 are expressly incorporated by reference herein.

1. A liquid crystal display comprising: a liquid crystal disposedbetween a first transparent substrate and a second transparentsubstrate; a first electrode and second electrode which overlie thefirst transparent substrate and which are used to drive the liquidcrystal; one or more layers overlying the first electrode; and one ormore layers overlying the second electrode, wherein the correlationbetween layers disposed between the first electrode and the liquidcrystal agrees with the correlation between layers disposed between thesecond electrode and the liquid crystal.
 2. A liquid crystal displaycomprising: a liquid crystal disposed between a first transparentsubstrate and a second transparent substrate; a first electrode andsecond electrode which overlie the first transparent substrate and whichare used to drive the liquid crystal; one or more layers overlying thefirst electrode; and one or more layers overlying the second electrode,wherein the amount of charge accumulated at the interface or interfacesbetween layers disposed between the first electrode and the liquidcrystal is substantially equal to the amount of charge accumulated atthe interface or interfaces between layers disposed between the secondelectrode and the liquid crystal.
 3. The liquid crystal displayaccording to claim 1, further comprising: a first inorganic layerextending over the first electrode; a second inorganic layer overlyingthe second electrode; and an alignment layer extending over the secondinorganic layer; wherein the second electrode includes linear portionsand slit portions alternately arranged on or above the first inorganiclayer.
 4. The liquid crystal display according to claim 3, whereinportions of the second inorganic layer are disposed only on the linearportions and the alignment layer extends over the first inorganic layer,the second electrode, and the second inorganic layer.
 5. The liquidcrystal display according to claim 3, wherein the second inorganic layerextends over the first inorganic layer, the linear portions, and theslit portions.
 6. The liquid crystal display according to claim 3,wherein the first and second inorganic layers are made of the samematerial.
 7. The liquid crystal display according to claim 3, whereinthe first and second inorganic layers contain at least one compoundselected from the group consisting of a nitrogen compound, and an oxygencompound.
 8. The liquid crystal display according to claim 1, furthercomprising: an organic layer which is made of an organic material havingan imide bond and which extends over the first electrode; and analignment layer made of an organic material having an imide bond,wherein the second electrode includes linear portions and slit portionsalternately arranged on or above the inorganic layer and the alignmentlayer extends over the organic layer, the linear portions, and the slitportions.
 9. The liquid crystal display according to claim 1, furthercomprising: an organic layer which is made of an organic material suchas polyamide and which extends over the first electrode; and analignment layer made of an organic material such as polyamide, whereinthe second electrode includes linear portions and slit portionsalternately arranged on or above the inorganic layer and the alignmentlayer extends over the organic layer, the linear portions, and the slitportions.
 10. The liquid crystal display according to claim 8, whereinthe organic layer and the alignment layer are made of the same material.11. The liquid crystal display according to claim 1, wherein the firstand second electrodes are transparent.
 12. A method of manufacturing theliquid crystal display according to claim 4, comprising: forming thefirst electrode on or above the first transparent substrate; forming thefirst inorganic layer over the first electrode; forming a transparentconductive material layer over the first inorganic layer; forming thesecond inorganic layer over the transparent conductive material layer;forming the second electrode in such a manner that the transparentconductive material layer and the second inorganic layer are patternedtogether such that the linear portions and the slit portions haveportions of the transparent conductive material layer and portions ofthe second inorganic layer and are alternately arranged; forming thealignment layer over the second electrode; and attaching the secondtransparent substrate to the first transparent substrate to seal theliquid crystal between the first transparent substrate and the secondtransparent substrate.
 13. The method according to claim 12, furthercomprising: forming an interconnect layer extending to a region which isdisposed on the first transparent substrate and which is used to form aterminal section; and forming an electrode over the interconnect layer,wherein the first inorganic layer is formed such that the firstelectrode is covered with the first inorganic layer and the electrode isexposed from the first inorganic layer, the transparent conductivematerial layer is formed so as to cover the first inorganic layer andthe exposed electrode, and the transparent conductive material layer andthe second inorganic layer are patterned together such that the secondelectrode remains and the second inorganic layer is partly removed fromthe electrode.
 14. A method of manufacturing the liquid crystal displayaccording to claim 5, comprising: forming the first electrode on orabove the first transparent substrate; forming the first inorganic layerover the first electrode; forming the second electrode on the firstinorganic layer; forming the second inorganic layer over the firstinorganic layer, the linear portions, and the slit portions; forming thealignment layer over the second inorganic layer; and attaching thesecond transparent substrate to the first transparent substrate to sealthe liquid crystal between the first transparent substrate and thesecond transparent substrate.
 15. The method according to claim 12,wherein the second inorganic layer is formed by at least one processselected from the group consisting of a chemical vapor depositionprocess, a coating process and a printing process.
 16. The methodaccording to claim 12, wherein the first and second inorganic layers aremade of the same material.
 17. A method of manufacturing the liquidcrystal display according to claim 8, comprising: forming the firstelectrode on or above the first transparent substrate; forming theinorganic layer over the first electrode; forming the second electrodeon the first inorganic layer; forming the alignment layer over theinorganic layer, the linear portions, and the slit portions; rubbing thealignment layer; and attaching the second transparent substrate to thefirst transparent substrate to seal the liquid crystal between the firsttransparent substrate and the second transparent substrate.
 18. A methodof manufacturing the liquid crystal display according to claim 9,comprising: forming the first electrode on or above the firsttransparent substrate; forming the inorganic layer over the firstelectrode; forming the second electrode on the first inorganic layer;forming the alignment layer over the inorganic layer, the linearportions, and the slit portions; rubbing the alignment layer; andattaching the second transparent substrate to the first transparentsubstrate to seal the liquid crystal between the first transparentsubstrate and the second transparent substrate.
 19. The method accordingto claim 17, wherein the inorganic layer and the alignment layer aremade of the same material.
 20. The method according to claim 17, whereinthe alignment layer is formed by printing an organic material.